Radiotelegraphic receiver



Patented Apr. 30, 1935 RADIOTELEGRAPI -IIG RECEIVER Yves Marrec, Le Vesinet, and Georges Armand Beauvais, Clamart, France Application October 15, 1931, Serial No. 568,920 In France October 16, 1930 4 Claims.

The main object of this invention is to provide 5 stable.

.It is well known that the reception by the beat methods (autodyne, heterodyne, superheterodyne) "of these emissions offers great difficulties;

The variations of frequency of the emission produce the same variations of the frequency of the beats, resulting in modifications of pitch of the sound (autodyne' or heterodyne) and in changes of amplification-if use is made of selective amplifiers (superheterodyne for instance).

The super-regeneration receivers already known transform the received electromagnetic waves of unstable frequency, into electric oscillations of constant frequency, and avoid the above mentioned inconveniences, but give rise to another inconvenience. In fact, if the frequency of modulation is audible, the note of modulation is permanently heard. The signals appear as a reinforcement or as a diminution of the intensity of this note of fixed pitch, but this continuous sound is very tiring in the absence of signals.

The invention provides for a reception of constant intensity, for completely eliminating all humming and like noises between the signals; and for ensuring the elimination of parasitic noises.

For these purposes, the invention is characterized by the combination in a single structure of two apparatus which are known but which up to now had been used separately, 1. e. on the .one

" hand, a super-regeneration receiver and, on the other hand, a filter having a sill eifect.

'By the expression filter having a sill effect is meant any apparatus which, energized by currents of different frequency and intensity, acts as a selecting relay, by producing a current of constant intensity under the action of the energization currents the intensity of which is above a' given limit, and giving no current under the action of energization currents having an intensity smaller than the above mentioned limit.

An example of such an apparatus is described in the French Patent No. 619.391, dated November 30th, 1925,'in the name of Yves Marrec; this example is described more in detail hereinafter. But it is obvious that any apparatus fulfilling the same function might be used, instead of that above mentioned, in the combination according to this invention.

Filters having a sill effect were used up to now for eliminating parasitic noises; in the new application according to the invention, although the filter having a sill effect continues to act for eliminating parasitic noises, it acquires quite a new function, which is to stop at the outlet of a super-regeneration receiven currents having 5 an intensity lower than a certain limit (which currents are those occurring between the signals) and the filter thus produces a new desirable result, which is theelimination of humming or like noises between the signals in a super-regeneration receiver. 1

The system of this invention consists essentially of a conventional type of super-regenerative receiver for reception of continuous wave telegraphic signals, and a filter system which takes the output of this receiver and acts upon it in such a manner that audio signals below a certain threshold Value are blocked and not permitted to reach the translating device. Such action prevents the occurrence in the translating device of the local oscillations and stray currents which would ordinarily cause disturbing noises in the translating device and thus materially depreciate the, quality of the radio telegraphic signal'reception. The invention obtains this desirable result or, in other words, avoids the commonly present undesirable noises/by the novel combination of the super-regenerative receiver and the cooperative filter system.

More specifically speaking, the invention comprises receiving telegraphic signals, such as interrupted continuous carrier waves, and detecting the received signals with a super-regenerative detector, modulated by an audible note. This note is then amplified in a filter which requires a predetermined impressed signal voltage to actuate it to pass the signal on to the reproducer such as a telephone.

The accompanying drawing illustrates, by way of example only, two'forms of carrying out the invention. a

Figure 1 is a diagram of the new combination according to the invention.

Figure 2 is a diagram of the Marrec filter, such as described in the French Patent No. 619.391.

Figure 3 illustrates a second form of carrying out the invention.

The device illustrated in Fig. 1 includes a superregeneration receiver comprising a modulating system M of musical frequency.

The aerial A engages through a'few turns S with the oscillatory circuit C L tuned on the wave to be received, the induction coil L being firmly coupled to the induction coil L so that the oscilr lations are easily generated in the circuit C L. The

plate of the corresponding valve P is supplied with modulated direct current, through the modulating system M by means of the induction coil S coupled to the modulating system; finally, a detector valve D is assembled by connecting its grid to that of the valve P through the medium of a condenser E of low capacity, the potential of this grid being controlled by the resistance R.

If the modulation of the superregeneration set is effected at audiofrequency, the note of this modulation will constantly be heard, but the signal will appear as a reinforcement or a diminution of the intensity of this note, the pitch of which remains fixed.

According to the invention, to hear signals only, to the exclusion of any humming or like noise, there is arranged in the plate circuit of the detector valve D an amplifying filter F having a sill effect, such for instance as the Marrec filter hereinafter described with reference to Fig. 2.

I, I designate the terminals for the incoming audio-frequency currents, 9 and Hi designate the three electrode, valves, suitably fed, of an aperiodic the transformers connecting the amplifying valves, two of which are'shown in the drawing at 9 and H3. H designates the heating rheostat of the amplifying valvesS and I0, for controlling the optimum energy sent into the resonantamplifying system constituted by the two electrode valves 52 and i3 shown on the right-hand side of the diagram and coupled through themedium of capacities l4, resistances l5 and induction coils I6 comprising variable magnetic circuits H, as well as through intermediate tappings on the induction coils simultaneously controlled by the twoway switch l8 and fixed tuning condensers I9. 20 designates the outlet terminals for the filtered currents, and 2| is the heating rheostat controlling the amplification and filtration. The telephone receiver T is connected to the terminals 20.

A switch 22 is arranged in such a manner that it can be placed either on a contact piece 23 putting the filter out of circuit, or on a resonance contact piece 24. When the switch is placed on the latter contact piece, the apparatus does not operate as a filter, but in a manner similar to the known resonance amplifiers. A third contact piece 25 permits utilizing the whole apparatus when the switching lever 22 is moved on to this contact piece 25.

.The aperiodic amplifying unit has the effect of giving to the signal the same intensity as that of the loud parasitic noises, by utilizing the eifect of saturation of the valves; the resonance amplifying unit has the effect of giving to the signalling currents an intensity higher than that of the parasiticcurrents of different frequency; moreover, the suitable adjustment of the heating'determines the sill effect, which consists in reducing to a null value the currents the intensity of which does not reach a definite minimum. In this way, the telephone T is affected by the signals only, to the exclusion of the parasitic noises and of the currents arising from the modulating systern M without the signals.

The example of Fig. 3 is constituted by the combination of an oscillating valve 26, of a detector valve 2i, of a modulating valve 28, of a low frequency amplifier valve 29 and of valves 30 and 3! of' the filter.

The aerialor collector 32 is connected to an aperiodic aerial induction coil 33; the tuning induction coil 34 of the grid circuit is coupled to this induction coil 33, and the plate induction coil 35 is coupled to the oscillatory grid circuit. The variable tuning condenser is shown at 36. The condenser 31 is the fixed detecting capacity, and 38 is a resistance serving to maintain the grid potential at a fixed value. The condenser 39 serves as a capacity for the modulating valve 28, and 46 the capacity of the modulating valve for the audiofrequency. 4| is an induction coil for coupling the oscillator valve 26 with the modulating valve 28, the plate induction coil of the 'valve 28 is shown at 42 and the grid induction coil at 43. The induction coils 44 are tuning induction coils having variable magnetic circuits, for

tuning of the audiofrequency of the modulating valve, these induction coils being associated with fixed capacities 45. The condensers 46 are the coupling capacities of the valves 30 and 3|, having circuits tuned on the modulating audiofrequency, and 4'! designates the resistances maintaining at a fixed value the grid potential of these valves arranged in tuned circuits.

An adjustable resistance 48 controls the heating of the modulating valve 28, and another adjustable resistance 49 controls the heating of the valves 35 and 3|, and consequently the clearne'ss of reception of the audiofrequency; A switch 50 provides for changing from inaudible superregeneration operation to audible superregeneration operation. i V

Finally, 5| designates the coupling transformer for the low frequency amplifying valve 29, and 52 is a jack adapted to receive a plug connected to the listening devices, and serving at the same time as general switch for heating the valves of the filter-modulator unit.

What we claim as our invention and desire to secure by Letters Patent, is:-

1. A radio receiver adapted to receive continuous wave telegraphic signals, comprising in combination, a super-regenerative receiver adapted to receive such signals and modulate them at an audio frequency, the output of said receiver being a continuous audio frequency current varying in amplitude in accordance with the signals, a filter connected to the output of said receiver having means for passing current of said audiofrequency above a predetermined threshold value of amplitude and for blocking current below said threshold value, whereby said audio frequency current is reflected in the filter output only during signalling periods, and a translating device connected to the output of said filter.

2. A radio receiver adapted to receive contin-' uous wave telegraphic signals, comprising in combination, a super-regenerative receiver adapted to receive such signals and modulate them at an audio frequency, the output of said receiver being a continuousaudio frequency current varying in amplitude in accordance with the signals, a vacuum tube amplifier connected to the output of said receiver adapted toamplify current of said audio frequency above a predetermined threshold value of amplitude and to block current below said threshold value, whereby said audio frequency current is reflected in said amplifier output only during signalling periods, and a translating device connected to the output of said amplifier.

3. A radio receiver adapted toreceive continuous wave telegraphic signals, comprising in combination, a super-regenerative receiver adapted to receive such signals and modulate them at an audio frequency, the output of said receiver being a continuous audio frequency current varying in amplitude in accordance with the signals, an audio frequency vacuum tube amplifier connected to the output of said receiver tuned to the frequency of said signalling current and adapted to amplify said signalling current selectively, said amplifier being adapted to amplify current of said audio frequency above a predetermined threshold value of amplitude and to block current below said threshold value, whereby said audio frequency current is reflected in said amplifier output only during signalling periods, and a translating device connected to the output of said amplifier.

4. A radio receiver adapted to receive continuous Wave telegraphic signals, comprising in combination, a super-regenerative receiver adapted to receive such signals and modulate them at an audio frequency, the output of said receiver being a continuous audio frequency current varying in amplitude in accordance with the signals,

an aperiodic vacuum tube amplifier connected to the output of said receiver adapted to be saturated by strong parasitic currents, whereby said parasitic currents are reduced in said amplifier output to substantially the same amplitude as said signalling current, an audio frequency vacuum tube amplifier connected to the output of said aperiodic amplifier tuned to the frequency of said signalling current and adapted to amplify said signalling current selectively, said tuned audio frequency amplifier being adapted to amplify current of said audio frequency above a predetermined threshold value of amplitude and to block current below said threshold value, whereby said audio frequency current is reflected in said amplifier output only during signalling periods, and a translating device connected to the output of said last-namedamplifier.

YVES MARREC. GEORGES ARMAND BEAUVAIS. 

